Air Pressure leak

[dilvoy]

I have an M35A2 and yesterday when I fired it up to take a load of scrap metal to the dump, it never built up more pressure than 60 PSI and the air warning buzzer kept buzzing. When I shut the engine off, I heard a loud hissing under he cab. It stops after about thirty seconds when the air pressure is depleted. I could not feel where any air was excaping from. Air pressure does make it into the two air tanks. I have isolated it to the Air Pack area, from the direction of the sound. Any guesses as to where my problem might be?

 

[scooter01922]

I have a similar leak at the momont, but the truck will still hold 90-100 PSI when running, but the tanks bleed drow in a min or 2. I know the leak is around the fitting into the airpac. Its the line closest to the frame rail and has several bends in it. Mine leaks past the actual sealing ferrule. I'm gonna need to check it closer later this week. I believe you will need a 15/16 wrench to try to tighten it, maybe its just loose. Sorry i can't be of more help, i'll let you know what fixes mine.

 

[Floridianson]

You could mix up some soapy water and apply with spray bottle for location.

 

[cleb]

On the airpack, frame side, there is an airline coming in, that goes to a flange, which is held to the airpack by 4 bolts. I had a slight air leak I could feel around that area. After tightening the four bolts equally, the leak went away. They are a bit hard to get to, patience is your friend. Taking the skid plate off will also help. The air seemed to be coming from the actual fitting the copper line went into, but it was really the flange leaking that made it seem that way. One other thing to check are the drain valves on the tanks. Mine were leaking slightly. After fixing those 2 things on my truck, she will hold 60-90psi overnight no problem.

 

[dilvoy]

Thanks for the tips guys, I'll be able to check things out this Sunday.

 

[dilvoy]

Well, I was up where I keep my vehicles yesterday and shure enough, when I fired up the deuce, the pressure maxed out at approx 60 psi. I needed to use my impact wrench so I hooked it up to do the job, just incase I made the air system inoperable, after my checking and tightening of fittings. Well...... after I did my job, the air pressure was up at 90 psi with no leaking (hissing) sound when I stopped the engine. Any ideas what might have happened? Is there a pressure pop off valve located very close to the Airpack?

 

[Barrman]

Another way to keep air in the system without running the engine is to use the emergency glad hand on the passenger side rear. Put fittings on it so you plug an air hose from your home compressor to the glad hand, open the valve and crawl under the truck to find the leak.

 

[dilvoy]

Hey, that's a great idea. I'll just take air pressure from one of the other deuces. This way I can have way more time to track down the leak, if it ever shows up again. I'll try slightly flexing any copper lines to see if anything happens when I have air from the other deuce hooked into this one.

 

[Barrman]

Look around the clamps holding the lines to the frame. Corroding clamps could have bit into the line or, soldier B could have undone the line at some place down the line, bent it out of the way for something and then bent it back. Never knowing he kinked it at the next clamp down the line.

 

[dlawbrey]

If you have an air compressor put air to the truck with it not running and you will have a constat supply of air and will be able to get under it and explore. Have fun.